ASPENS AND WILLOWS
Article #71, May, 2003
By Bill Cook
Aspens and willows are related to each other as members of the Salicaceae family. In the Upper Peninsula, there are ten tree species, making the Salicaceae the third largest tree family in the region, with about twelve percent of the timber volume. Only the Rosaceae (cherries, juneberries, hawthorne, mountain ash) and Pinaceae (pines, spruces, firs, tamarack, hemlock) have more species.
Family members have separate male and female trees, which is especially good to know if you are a ruffed grouse, which prefer the male flower buds. The catkins, or aments, mature early in the spring. Very light, windborne seeds are ready to sail by late spring or early summer, sometimes prolific enough to resemble a light snow. “Cottonwood” gets its name from these fluffy seeds.
Quaking aspen and bigtooth aspen are common in our forests, often called “popple”. Aspens provide valuable wildlife habitat, erosion control, and fiber resources. The light gray bark often results in their misidentification as paper birch. Both species have flattened leaf stems, causing the characteristic flutter in even the lightest of breezes. Aspen require full sunlight to reproduce and grow, making clearcutting a necessary, but controversial, management practice. Thousands of root suckers per acre usually produce a new forest quickly.
Balm-of-Gilead and cottonwood are close cousins to the aspens. Balm tends to inhabit the fringes of wetlands and cottonwood prefers riverside habitat. Balm is a rather resinous tree, especially the long, pointy buds. Cottonwood grows the largest diameter trees in the region, sometimes several feet across.
Two imported “aspens” include Lombardy poplar and white poplar, both European in origin. The Lombardy poplar grows in a characteristic column, popular for a while as an ornamental. The white poplar was also introduced as an ornamental, but the vigorous sprouting habit frustrates many homeowners. Both are most commonly found in residential settings and on old farms.
Among the willows, only the black willow regularly reaches tree size, and can grow quite large in a relatively few number of years. Many of the large trees along lakes and wetlands are black willow. A very vigorous sprouter, black willow can even re-establish itself from cut lengths of trunk.
Several other willow species sometimes attain tree form, notably Bebb’s, bay-leaved, and peachleaf willow. Bebb’s is one of the state’s most common willows. The scruffy large shrubs/small trees found on most soils can be easily identified by the bark. Bay-leaved willow can reach 30-40 feet in Gogebic County. Peachleaf willow is more common in the Lower Peninsula, but can be found in the southern U.P.
In addition to the four willows mentioned, there are an additional 17 species of shrubs. Pussy willow may be the best known and is very common throughout the state. “Diamond” willow is not a species, but rather a growth pattern formed by a fungus that infects a number of willow species. Many willows easily hybridize and identification can be challenging.
The Salicaceae sport only two genera around the world (aspens and willows) but have roughly 335 species. Most live in the Northern Hemisphere and about 120 live in North America.
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Bill Cook is an MSU Extension forester providing educational programming for the entire Upper Peninsula. His office is located at the MSU Upper Peninsula Tree Improvement Center near Escanaba. The Center is the headquarters for three MSU Forestry properties in the U.P., with a combined area of about 8,000 acres. He can be reached at email@example.com or 906-786-1575.
by Bill Cook, Forester/Biologist, Michigan State University Extension, 6005
J Road, Escanaba, MI 49829
906-786-1575 (voice), 906-786-9370 (fax), e-mail: firstname.lastname@example.org
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